The ends of electric cables have to include connecting elements, such as different types of terminals, in order to provide connections that depend on the applications.
Nevertheless, the mode of fixation always remains the same and consists in a deformation of one part of the terminal, forming a sleeve in which a cable is preferably inserted. This deformation action is called crimping.
The dimensions of the terminals vary according to the applications, but remain of necessity reduced, because the pair of pliers is operated by hand.
On the other hand, the applied force required for obtaining a good quality crimping of terminals on the cables remains important and an arrangement of levers is provided for these pliers for multiplying the manual force applied by the operator.
Known from U.S. Pat. No. 2,814,222 is a pair of crimping pliers that consists of a movable jaw and a multiplying lever.
This pair of pliers is simple, but the straight upper arm supports all of the stresses generated by the pressure of the movable jaw and the axis of rotation of the movable jaw is subjected to strong stresses. The crimping force is weakly multiplied.
In general, the tools of most recent prior art, particularly those described in the patent applications EP A 536,641 and EP A 536,652 comprise one arm, the end of which constitutes a fixed jaw, and a second arm, which operates, through a system of levers, a movable jaw that rotates around a pivot point that is an integral part of the first arm; when the operator squeezes the arms, this causes the movable jaw to come against the fixed jaw with a considerable squeezing force.
Any element interposed between the two jaws is subjected to the multiplied squeezing force obtained through the system of levers.
Moreover, known from U.S. Pat. No. 5,280,716 is a tool of the general type above, the two arms of which are joined to each other through an articulated hinge link on, on the one hand, a fixed axis that is an integral part of the arm bearing the fixed jaw and, on the other hand, a movable axis in an oblong opening placed in the other arm.
In a likewise known manner, the fixed jaw can be advantageously furnished with a turret that bears a number of indentations with a means of indexing this turret so that the desired indentation is maintained with respect to the movable jaw during the squeezing action.
Provided for in the known arrangements is a strong multiplication but a small opening of the jaws, which is not particularly adapted to the operator, especially when, prior to crimping, the terminals display a considerable diameter. On the other hand, it is appropriate to reduce the opening of the arms in order to make the manipulations more practical.
Moreover, it is necessary to avoid having the stresses at the level of the pivot point greater than the forces transmitted at the level of the jaws themselves, because, in this case, the efficiency is not optimal.
These pliers are made of light metallic materials, such as aluminum alloys, so as to attain a compromise between the different factors such as cost/quality/performance.
In order to improve these factors still further, it has been provided that such pliers be made of composite materials, such as fiber-loaded or fiber-reinforced polymer compositions.
Nevertheless, particularly in the case of a composite material realization, it is necessary to pursue several objectives and, with this aim in view, the present invention proposes a pair of crimping pliers that makes it possible, in particular:                to reduce the stresses perpendicular to all pivot points to a value that is less than that of the force exerted at the level of the jaws;        to produce a significant opening of the jaws for a given multiplied force, but a limited opening of the arms; and        to retain a significant multiplied force so as to ensure a good quality of crimping.        